1. Field of the Invention
The present invention relates generally to a fixing device using the induction heating, which is used for fixing an image, such as a toner image, on a fixed material, such as a paper, in an image forming system, such as an electrophotography system, an electrostatic process copying machine or a laser printer.
2. Related Background Art
Conventionally, there is known the following fixing device for an electrophotography system. That is, a halogen lamp or the like is used as a heat source. This is provided inside of a heating roller of a metal to heat the heating roller. A pressure roller having an elastic material at least on the surface thereof is provided so as to face the heating roller while pressingly contacting the heating roller. A paper serving as a fixed material is caused to pass through a nip portion formed between the two rollers contacting each other. During the passing, a toner image on the paper is melted and fixed. There is also known a fixing device wherein a flash lamp is used for heating a paper without contacting the paper to fix a toner image. Moreover, as fixing devices having improved efficiency, there are known a fixing device having magnetic field producing means combined with a belt as shown in Japanese Patent Laid-Open No. 8-76620, and a fixing device using a heating member of a ceramics as shown in Japanese Patent Laid-Open No. 59-33476.
However, there are various problems in the above described conventional fixing devices. That is, in the fixing device utilizing the induction heating based on an induction coil, it is actually very difficult to uniformly heat the heating roller. In order to optimize the heating efficiency to realize the uniform heating, it is required to optimize the construction of the induction coil itself, but this is actually remarkably difficult.
With respect to the uniform heating of the heating roller, it is also required to prevent the non-uniformity of temperature of the heating roller in axial directions (cross directions) thereof. The conventional device using the halogen lamp heater is designed to cope with it by changing the light distribution characteristics. Also in the induction heating fixing devices, it is required to take measures to obtain the same effects.
Comparing the induction heating coil with the coil of the existing motor or the like, the working environment of the induction heating coil is greatly different from that of the coil of the existing motor or the like. Therefore, unlike the coil of the motor or the like, the shape of the induction heating coil must be selected particularly in view of heat resistance.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a light and inexpensive fixing device for an electrophotography system or the like, the fixing device using an induction heating device (coil), to which a great electric power is supplied to be necessarily heated to a high temperature, and a heating roller heated by the induction heating device, the fixing device having excellent heat resistance, heat radiating performance and insulation performance, and the fixing device being capable of heating the heating roller uniformly and adequately on the basis of the relationship between the positions of the heating roller and a fixed material.
In order to accomplish the aforementioned and other objects, according to one aspect of the present invention, there is provided a fixing device using induction heating for causing alternating current to pass through electromagnetic induction coils, which are arranged so as to be close to an endless member having a metal layer of a conductive material, to cause the endless member to generate heat to heat a member to be fixed, wherein the fixing of the electromagnetic induction coils to each other and the fixing of the core to the coils are carried out by an adhesive material mixed with mica.
According to another aspect of the present invention, there is provided a fixing device using induction heating for causing alternating current to pass through an electromagnetic induction coil, which is arranged so as to be close to an endless member having a metal layer of a conductive material, to cause the endless member to generate heat to heat a member to be fixed, wherein the electromagnetic induction coil is wound onto a core of a non-magnetic material coated with a resin or paint.
According to another aspect of the present invention, there is provided a fixing device using induction heating for causing alternating current to pass through an electromagnetic induction coil, which is arranged so as to be close to an endless member having a metal layer of a conductive material, to cause the endless member to generate heat to heat a member to be fixed, wherein the coil is wound around a first axis, and the coil thus wound is fixed by winding a heat resistant bundling band onto the coil around a second axis substantially perpendicular to the first axis.
According to another aspect of the present invention, there is provided a fixing device using induction heating for causing alternating current to pass through an electromagnetic induction coil, which is arranged so as to be close to an endless member having a metal layer of a conductive material, to cause the endless member to generate heat to heat a member to be fixed, wherein the coil is wound around a first axis, and the coil thus wound is fixed by a molded body of a heat resistant material having a member wound onto the coil around an axis perpendicular to at least the first axis.
According to another aspect of the present invention, there is provided a fixing device using induction heating for causing alternating current to pass through electromagnetic induction coils, which are arranged so as to be close to an endless member having a metal layer of a conductive material, to cause the endless member to generate heat to heat a member to be fixed, wherein a heat resistant, insulating and heat conductive sheet for providing both of heat radiation and insulation of the coils is provided on the surfaces of the coils.
According to another aspect of the present invention, there is provided a fixing device using induction heating for causing alternating current to pass through an electromagnetic induction coil, which is arranged so as to be close to an endless member having a metal layer of a conductive material, to cause the endless member to generate heat to heat a member to be fixed, wherein the coil is wound onto a core of a non-magnetic material, and a heat resistant, insulating and heat conductive sheet for providing both of heat radiation and insulation of the coils is provided between the surface of the core and the coil.
According to another aspect of the present invention, there is provided a fixing device using induction heating for causing alternating current to pass through an electromagnetic induction coil, which is arranged so as to be close to an endless member having a metal layer of a conductive material, to cause the endless member to generate heat to heat a member to be fixed, wherein the center of the coil in axial directions is offset from the center of the endless member, which serves as an object to be heated, in axial directions in accordance with thermal load of the endless member.
According to another aspect of the present invention, there is provided a fixing device using induction heating for causing alternating current to pass through an electromagnetic induction coil, which is arranged so as to be close to an endless member having a metal layer of a conductive material, to cause the endless member to generate heat to heat a member to be fixed, wherein the coil is wound onto a core of a non-magnetic material, and the core has a hole extending in directions substantially perpendicular to the axis of the core.
According to a further aspect of the present invention, there is provided a fixing device using induction heating for causing alternating current to pass through an electromagnetic induction coil, which is arranged so as to be close to an endless member having a metal layer of a conductive material, to cause the endless member to generate heat to heat a member to be fixed, wherein the coil is wound onto a core of a non-magnetic material, and the core has a first hole extending in the axial directions of the core.
According to a still further aspect of the present invention, there is provided a fixing device using induction heating for causing alternating current to pass through an electromagnetic induction coil, which is arranged so as to be close to an endless member having a metal layer of a conductive material, to cause the endless member to generate heat to heat a member to be fixed, wherein the coil has a plurality of unit wires, each of which comprises a conductor coated with a first insulating coating, and the plurality of unit wires are coated with a second insulating coating to doubly isolate the coil from the endless member.